1. Field of the Invention
The present invention relates to dynamic semiconductor memory devices, and more particularly, to a dynamic random access memory (DRAM) that can store information in its capacitor.
2. Description of the Background Art
FIG. 18 schematically shows a row decoder and a memory cell array of a DRAM.
Referring to FIG. 18, an externally applied row address to a semiconductor memory device is internally held to become internal row address signals INTA0-INTAn to be applied to a row decoder 722. Row decoder 722 decodes internal address signals INTA0-INTAn to output a word line activation signal that activates any one of word lines WL0-WLn. Here, a conventional semiconductor memory device connects one memory cell with a bit line (not shown) to amplify the data, whereby the data is read out in binary of an H logical high) level or an L (logical low) level.
It is desirable in a small type information equipment that is driven by a battery such as a portable terminal for the semiconductor memory device to consume lower power in a resume or suspend state than in a normal usage state where the user is operating the terminal. Lengthening the refresh cycle of the stored information in the DRAM is one approach. For this purpose, the capacitance of the capacitor per one memory cell in the DRAM should be increased. In a resume or suspend state, lower power consumption is more desirable than a large storage capacity for a semiconductor memory device functioning as the main memory.
In contrast, a larger storage capacity is more desirable for the main memory in the normal usage state where the user is operating the terminal.
Increasing the capacitance of the capacitor per one memory cell in a DRAM and increasing the storage capacity both cause increase in the chip area of the DRAM. In applications where low power consumption is required for the small type information equipment, there were a problem that either increase in the storage capacity of the memory or reduction in the storage capacity of the memory to increase the driving period of time of the battery in a resume or suspend state must be selected.